NBA Great Wilt Chamberlin Stamp (Credit: United States Postal Service)

Wilt Chamberlain captured America’s imagination for two decades. With his 7-foot-1 frame, his commanding presence on the basketball court, his ability to rebound and score and his astounding athleticism, he became one of the most memorable players in NBA history.

Now, Chamberlain, the only man to score 100 points in an NBA game, will become the first player from the league to be honored with a postage stamp in his image. And fittingly enough, the two versions being issued by the Postal Service are nearly two inches long, or about a third longer than the usual stamp.

It would not be right any other way for the player known as Wilt the Stilt and alternately as the Big Dipper. Chamberlain died in 1999 at 63, but his name still resonates in the sport. And even at its atypical size, the new stamp could barely contain Chamberlain’s dimensions. “We still had trouble fitting him into those proportions,” said Kadir Nelson, the artist who painted the images.

Nelson created two versions of the stamp. One shows Chamberlain in the act of shooting with his first NBA team, the Philadelphia Warriors, for whom he started playing in 1959. The other depicts him rebounding for the Los Angeles Lakers, his final club, for whom he played from 1968 to 1973.

The ceremony comes at a frustrating time: The 76ers avoided tying the record for the worst start to a season in NBA history Wednesday night when they ended their 0-17 run with a victory at Minnesota.

But for a few minutes Friday night, Philadelphia fans old enough to remember can think back to the days when Chamberlain — first as a Warrior and later as a 76er — engaged in epic battles with the Boston Celtics’ Bill Russell. In 1967, Chamberlain led Philadelphia to an NBA title, the first of two in his career.

But just how did Chamberlain end up on a stamp?

The creation of a postage stamp is a process that takes years and begins with the Citizens’ Stamp Advisory Committee, a volunteer group appointed by the postmaster general. The committee evaluates roughly 40,000 proposals annually before recommending about 30 people or subjects for the postmaster general’s review.

A Chamberlain stamp was originally envisioned as part of a set of four basketball players who made history, said William J. Gicker, the creative director for the stamp program. A campaign engineered by Donald Hunt, a sportswriter for The Philadelphia Tribune, in support of Chamberlain led to thousands of letters and petition signatures being delivered to the committee.

“We were hoping for 2012,” Hunt said, “because that was the 50th anniversary of Wilt’s 100-point game.”

That didn’t happen, but by July 2013, Nelson presented the Postal Service with artwork of “early Wilt” and “later Wilt.” The citizens’ committee approved the images a year later.

“People loved them both,” said Antonio Alcalá, a Postal Service art director, “so we decided to do them both.”

Nelson said: “I think it was a good move because of his evolution as a player. As a young guy, he was mostly an offensive player. Then he became more of a defensive-oriented player.”

In all, about 50 million Forever stamps of Chamberlain, identified simply as Wilt in capital letters, will be printed. “It’s what we consider to be one of our blockbusters, so we do a little bit more than we normally do,” said Cindy Tackett, the acting director of stamp services for the Postal Service.

It will be a coup of sorts for Nelson, whose vibrant, expressionistic paintings often focus on African-American experiences.

Nelson was born in Silver Spring, Md., and eventually enrolled at Pratt Institute in Brooklyn, ostensibly to study architecture. He switched his major to illustration, and after graduating he got his first big break helping to draw scenes for the 1997 film “Amistad,” directed by Steven Spielberg.

He then teamed with the actress and dancer Debbie Allen on a children’s book, “Brothers of the Knight,” and her friends Spike Lee and Will Smith enlisted him for similar projects. Awards followed.

“I didn’t plan to do children’s books,” he said, “but one thing led to another.”

“Children’s books introduce art to children,” added Nelson, 40, the father of three. “It’s usually the first time they look at art. Kids think very visually — everything is larger than life — so it goes hand in hand with their development.”

At Pratt, Nelson had painted baseball players from the Negro Leagues, which piqued his interest in the sport’s lore. He traveled to the Negro Leagues Baseball Museum in Kansas City, Mo., and met the former player and manager Buck O’Neil.

Nelson’s conversations with O’Neil helped lead to a 2008 book, “We Are the Ship: The Story of Negro League Baseball.”

By then, Nelson was receiving regular commissions from the Postal Service. He gets biographical information from its art directors, and then drafts pencil-on-paper sketches. The initial renderings are rough, he said, because “I like to discover as I go and save the spontaneity for the finished piece.”

He paints the final version in color using oils. Graphic details, including the subject’s name, are added later.

“It’s very humbling,” he said, “because you’re creating a piece of history that’s permanent. You want to get it right because you can only do it once.”

Nelson revisited the subject of the Negro Leagues in 2010 with two stamps. He then painted a set of four stamps that saluted Joe DiMaggio, Larry Doby, Ted Williams and Willie Stargell. Last year, Nelson illustrated a stamp honoring the tennis champion Althea Gibson. He also painted images of the fiction writers Richard Wright and Ralph Ellison for stamps.

Nelson said that after 15 years of painting baseball scenes from the Negro Leagues he was ready to move on from that subject. Inspired in part by Chamberlain, he acknowledged that the idea of visually exploring the early days of professional basketball and teams like the all-black New York Renaissance was intriguing.

“I really love the history of sports and telling those stories,” Nelson said. “I like to see what the game looked like in its early, gritty style.”